Process of carburizing steel plates.



PATENTBD MAR. 7, 1905.

A. F. MITCHELL. PROCESS OF CARBURIZING STEEL PLATES.

APPLICATION FILED MAR. 17, 1904.

2 BHEBTS-SHBBT 1.

gnmmtoz wihmowo PATENTED MAR. ,7, 1905.

A. P. MITCHELL. PROCESS OF GARBUBIZING STEEL PLATES.

APPLICATION FILED MAR.17. 1904.

2 SHEETS-SHEET 2.

@wmdoz JZn/Jww V i/Vi? macaw ni'rnn Sterne Patented March 7, 19053.

PATENT SEVEN-TWENTIETITHS TO \VlLLlAM H. J ONES,

SYLVANIA.

OF HOMES. El-U), PENN- PROGESS OF CENFTHURIZING STEEL PLATES.

SPECIFICATION forming part of Letters Patent No. 784:,1'71, dated March 7, 1905.

Application filed March 17, 1904. Serial No. 198,648.

To all 1071 0112, it may concern:

Be it known that 1, ANDREW F. Mrroi-inLn, a

citizen of the United States, residing at Homestead, in the county of Ailegheny and State of Pennsylvania, have invented certain new and useful Improvements in Processes of Carburizing Steel Plates; and I do declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relatesto improvements in processes for carburizing steel plates, and par ticularly steel armor-plates.

x 5 The object of my invention is to improve and simplify processes of this character, and thereby render them more rapid and eflicac'ious and at the same time less expensive.

In the accompanying drawings, Figure 1 is a vertical longitudinal sectional view through a furnace with several sets of steel plates mounted therein and adapted to be carburized in accordance with my invention. Fig. 2 is a plan view of a set of two steel plates ready to be carburized. Fig. 3 is a sectional view, on an enlarged scale, taken on the line 3 3 of Fig. 2. Fig. 4 is a view similar to Fig. 2, showing how irregular-shaped portions of the steel plates may be carburized without afi'ecting 0 the remaining portions. Fig. 5 is a sectional view taken on the line 5 5 of Fig. 4. Fig. 6 is a view similar to Figs. 2 and 4-, illustrating another way in which certain portions of the steel plates may be carburized without affecting the remaining portions of the same. Fig. 7 is a sectional view taken on the line '7 T of Fig. 6.

Referring to the drawings by numeral, 1 denotes a heating-furnace of well-known con- 4 struction, having gas-ports 2 and 3 on each side through which the heating-gas enters and out of which it passes. The ends of the said furnace are provided with sight-openings or peep-holes t, and the hearth 5, which is constructed of lire-brick or other suitable material, is built upon a movable furnace bottom or truck 6.

1n the practice of my invention I arrange the steel plates in pairs or sets of two with their faces which are to be hardened or car- 5 burized juxtaposed and with a carbonaceous material in solid form confined between them by means of spacing bars or frames, as shown. The steel plates being thus arranged in pairs or sets form boxes, which may be placed in the furnace singly or in groups, according to the capacity of the furnace. In Fig. 1 I. have shown the furnace filled with four sets or boxes (denoted by the numeral 7) and arranged in two groups or tiers, each group or tier hav- 6O ing its upper set or box supported upon its lower one. in said Fig. 1, 8 denotes the lower steel plate of each set or box. 9 denotes its upper plate. 10 denotes the carbonaceous material, preferably in solid form, and 11 de- 5 notes the spacing bars or frames interposed between said plates 8 and 9. The plates 8 of the lower sets or boxes are supported and spaced from the hearth by blocks or supports 12 of lire-brick or other suitable material, and 7 the COIIOSIJOHLllDg' plates of the upper sets or boxes are supported and spaced from the up per sides of the upper plates 9 of the lower sets or boxes by similar blocks or supports 13, as shown.

ln constructing each set or box the lower plate 8 is iirstsuitably supported and the spacing bars or billets 11, preferably of steel, are then arranged around and adjacentto its edges,

indicated in Figs. 1, 2, and 3. After these 30 bars are luted by lire -c]ay li or the like in position upon the upper face of said plate 8, which face, as previously stated, is the one to be carburized, the solid carbonaceous material 10 is then put in so that it stands slightly 5 above the upper edges or faces of the bars 11, as clearly seen in Fig. 3. The upper plate S) is then placed upon said material with its face which is to be carburized down, and it is finally luted, as shown at 15, to said bars 11, so that 9 an air-tightbox is formed, the upper and lower plates forming the top and bottom and the bar 11 forming the sides.

In Figs. 1, 2, and 3 the plates 8 and 9 are square or rectangular and the bars ll are straight, being secured at or adjacent to the carburized.

edges of the plates; but it will be understood that the plates may be of any shape and that by making the bars 11 curved, as shown at 16 in Fig. 4, or irregular in shape any desired portion of the plates may be carburized. The said bars 11 along the sides and ends of the plates are preferably integral; but they may i be separate-that is, in the form of an open frame of rectangular or other shape. When it is desired to carburize only a portion of the plates-for instance, one end, as seen in Figs. 6 and 7-the bars 11 are secured, as shown, upon said end, and sag-blocks 17 are placed between said plates at their opposite ends to hold the upper plate as straight as possible. If it is desired to leave a central portion of the plate uncarburized that is, if it is desired to carburize all around a certain portion of the platethat portion is surrounded by a frame or by bars 18, as shown in Figs. at and 5, and the space within said bars 18, which form a surrounding frame or box, is filled with silicasand 19 or other suitable material.

It will be observed that by arranging and mounting the plates in the furnace as shown and described the flames and heating gases will have access to all parts of the outside of the plates except the small portions protected by the ends of the supporting-blocks. The result of this is that the plates can be brought to the required heat and the desired results obtained much more quickly than by the use of any of the present processes in which solid carbonaceous material is used.

It is to be noted that by my process the exterior surfaces of the plates are exposed to the direct heat in the furnace, and a high temperature is developed and constantly maintained,which quickly permeates the plates and carburizing material. In other processes the external surfaces of the plates are covered with fuel and it takes a considerable time for the required heat to reach the surface to be In the processes of this character heretofore practiced the usual time required to carburize two plates of average size was four hundred hours. Considerable time is saved in my method of preparing the plates for caburization. Moreover,a further saving in time is attained by my process in stripping the plates. In former processes from fortyeight to one hundred and twelve hours were required for this step in the process, whileI am enabled to strip the plates at once after carburization.

Itis obvious that the plates,as described, can be prepared upon the floor and afterward placed upon the supports in the furnace. It will thus be seen that it is possible to keep the furnace in constant use, as the plates may be drawn as soon as carburized and other plates previously prepared immediately placed therein while the furnace is hot. Another point in the use of my process is that more plates can be old methods of carburizing are used. This method of carburizing several sets of plates together in the same furnace is an important improvement over the present methods of two plates at a time. It will also be plain that the carbonaceous material, owing to its being in excess and projecting above the side and end bars, will support the upper plate, and thus prevent sagging or the formation of drops of molten metal called warts on the under side. In this connection it also of advantage to have an excess of carbonaceous material on account of the fact that the space between the bars and the plates affords room for suflicient luting material to render the box formed practically air-tight, and even if a small quantity of air should enter the excess of carburizing material would allow of slight burning without injuring the effectiveness of the process. It will thus be seen that my process is superior to the use of a brick box surrounding one or two plates with carbonaceous material next to the surface or surfaces to be carburized. A further advantage is that while I am carburizing the body of one side of each plate the edges remain soft or are non-cemented, thus making the machining of the plates comparatively easy. It is a well-known fact that when plates are hardened in water or other cooling liquid after having been carburized the edges will crack and break off. Especially is this the case when theplate has been bent. Hence it will be seen that on account of the edges remaining in their normal state this defect is eliminated. I do not desire to confine this noncementation to the edges alone; but at any time the operator may desire to carburize a portion of the plates only he may adjust the bars accordingly and place a solid carburizing agent between said bars which form the box, so that the portion of the plate that the bars are resting-on and luted to and the portion that is outside of the frames of the outer box will remain soft. Furthermore, my invention also provides a method whereby any desired part of the plates inside of the outer frames may remain non-cemented by the addition of suitable frames or bars forming a box at the desired place and filling the same with a noncementing material, such as silica-sand or the like. The frames or bars will act in this case as a wall or a separating device and hold the non-cementing and carbonaceous materials in their places. The expense in connection with using steel bars or frames for these purposes is very small, as they can be used a number of times.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is

1. The process of carburizing armor-plates, which consists in supporting a plate upon refractory material, arranging upon the upper face of said plate a sectional frame or box for placed in the same-sizedfurnacethan when the confining the carbonaceous material, luting "ream the lower edges of the frame-sections with refractory material, placing suflicient carbonaceous material within the frame to extend above the upper edge thereof, placing another plate upon the carbonaceous material, luting the upper edges of the frame, between the frame and the upper plate, and submitting plates thus prepared to heat in afurnace, sub stantially as described.

2. The process of carburizing portions only of armor-plates which consists in arranging between two plates inclosed compartments containinga non-cementing material, and then inclosing the entire surfaces to be carburized by a sectional frame containing suflicient carbonaceous material to extend above and below the frame, luting the upper and lower edges of the frame, and submitting the plates thus prepared to heat, whereby the edges of the plates and the portions submitted to non-cementing material will be uncarburized, for the purposes described.

3. The process of preparing armor-plates for carb'urization which consists in inter-posing ANDREW F. Ml'lOHELL. Witnesses:

WM. H. Jones, OTTO Os'rrrorr. 

